The present invention relates to airbag sensors which monitor the deployment sequence of an airbag with a tape which is pulled out of the cartridge by an end of the tape which is attached to the inside surface of the airbag.
Airbags, originally developed as a passive restraint system, work best in combination with seatbelts and other safety systems. Various systems have been developed to detect an xe2x80x9cout of positionxe2x80x9d vehicle occupant. Sensor systems designed to detect the vehicle occupant""s position often require constant monitoring so that in the event of a crash the vehicle occupant""s position is known. Sensor systems designed to detect the position of the vehicle occupant have been proposed based on ultrasound, optical, or capacitance sensors.
A simpler type of sensor such as shown in European Patent application EP 0990567A1, employs a plurality of tapes which extend between the front of an airbag and a tape dispensing cartridge mounted on the airbag housing. Tape extraction sensors within the cartridge monitor the rate at which tape is withdrawn from the cartridge and thus can detect airbag impact with a vehicle occupant by a decrease in airbag velocity. Improvements are needed to the known tape cartridges to facilitate installing the cartridges in an airbag module without allowing the tape to be prematurely drawn out of the cartridge.
The airbag deployment sensor of this invention has a cartridge which stores a quantity of tape that is drawn out of the cartridge during airbag deployment by one end of the tape which is attached to the inside surface of the airbag. In order to facilitate assembly of the cartridge into an airbag system, the cartridge is designed with a means for preventing tape from being prematurely extracted from the cartridge during the assembly process. The cartridge is used in combination with a mounting bracket designed to assure that the tape is free to be extracted from the cartridge once the cartridge is mounted to the bracket. A first embodiment employs a screw or key, which biases a brake member within the cartridge against the tape to prevent it from being extracted. The first embodiment can be used with a mounting bracket that will not allow the cartridge to be mounted so long as the screw or key, which functions to lock the tape within the cartridge, is in its locking position. A second approach is to use a spring biased locking member that biases a brake member within the cartridge against the tape to prevent the tape from being extracted. The second embodiment is used in conjunction with a mounting structure which engages the locking member so as to release the locking member, rendering it inoperative when the cartridge is installed to the mounting structure. A third approach employs the same principle as the first approach but is used with a cartridge that contains a spool on which the tape is wound. A key locks the spool against rotation so preventing tape from being prematurely drawn from the cartridge. Again the cartridge can be used with a mounting structure or bracket which prevents the cartridge from being mounted if the key is in the locking position. A fourth approach, which is similar to the second approach, uses a spring biased member that is biased to a position which prevents a spool from rotating. When the cartridge is installed the mounting structure compresses the biasing spring so that the spring no longer prevents rotation of the spool.
It is a feature of the present invention to provide a cartridge from which a tape is drawn during airbag deployment to measure the rate at which the airbag is deployed, wherein the tape is locked against withdrawal during airbag assembly, but when installed in the airbag module housing the tape can be withdrawn.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.
FIG. 1 is a schematic cross sectional view of an undeployed airbag showing the arrangement of a tape cartridge according to the present invention and its mounting bracket.
FIG. 2 is an exploded isometric view of the tape dispensing cartridge.
FIG. 3 is a cross-sectional view of a locking mechanism of an alternative embodiment tape dispensing cartridge according to the present invention, shown with the tape locked in position.
FIG. 4 is a cross sectional view of the locking mechanism of FIG. 3 mounted to a bracket such that tape can be withdrawn from the tape dispensing cartridge.
FIG. 5 is an exploded isometric view of tape dispensing cartridge of FIG. 3
FIG. 6 is a top plan view, partially cut away in section of a further alternative embodiment of the tape dispensing cartridge of this invention.
FIG. 7 is a side elevational cross-sectional view of the tape dispensing cartridge of FIG. 6 taken along section line 7xe2x80x947
FIG. 7A is a side elevational cross-sectional view of the tape dispensing cartridge of FIG. 7 shown installed on a bracket.
FIG. 8 is an exploded isometric cross-sectional view, partially cut away in section of yet another tape dispensing cartridge of this invention, wherein a tape spool is locked against rotation.
FIG. 9 is an isometric cross-sectional view of the tape dispensing cartridge of FIG. 8 wherein the tape spool is free to rotate.